title: A further microchromosome with centromeric association.
abstract: A 46,XY/47,XY,+mar karyotype was found in a 5-year-old boy with mental retardation and minor dysmorphisms. The marker was present in 68% of lymphocyte metaphases, was about the size of Yp, appeared pale with G- and C-bands and had a single pair of centromeric dots; it was never seen in two or more copies and appeared larger and clearly annular in a few cells. This microchromosome was associated (interchromosomal distance equal to or smaller than 18p) with any other chromosome(s) in 295/344 cells. Among a total of 457 associations, 240 (52%) were centromeric. Such a proportion as well as the mostly random distribution of centromeric associations was similar to 3 previous instances. The paucity of markers with centromeric association may reflect a relative unawareness on the subject but more probable indicates that such a phenomenon is confined to nonsatellited, monocentric and annular microchromosomes.
authors.affiliation: División de Genética, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco, México.
authors.forename: H
authors.initials: H
authors.lastname: Rivera
authors.forename: M G
authors.initials: MG
authors.lastname: Dominguez
authors.forename: A I
authors.initials: AI
authors.lastname: Vasquez
authors.forename: G
authors.initials: G
authors.lastname: Mejia-Baltodano
mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics*; D002503:Centromere; D002675:Child, Preschool; D002869:Chromosome Aberrations / Q000235:genetics*; D002871:Chromosome Banding; D005819:Genetic Markers; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics*; D008297:Male; D008677:Metaphase / Q000235:genetics
chemical_list: D005819:Genetic Markers